f.pier
Posts: 1405
Joined: Fri Aug 25, 2000 2:50 am

FR 738 Take Off

Sat Nov 15, 2003 9:36 pm

I sincerely don't know if it's only a Ryanair procedure, but I realized that every time the plane is at the beginning of the runway, ready to take off, the pilots add thrust to the engines, then they reduce it quite a lot, and finally they increase the power for the takeoff.

Is it a normal procedure or it's only a Ryanair procedure?

Why they do this?
 
fritzi
Posts: 2598
Joined: Sat Jun 30, 2001 2:34 am

RE: FR 738 Take Off

Sat Nov 15, 2003 11:21 pm

I think its standard procedure with all opperators.

First you get the engines stabalized at around 40% N1, then you throttle up to the desired amount of thrust for the takoff.
 
cancidas
Posts: 3985
Joined: Thu Jul 03, 2003 7:34 am

RE: FR 738 Take Off

Sun Nov 16, 2003 1:01 am

on airbus a/c, you need to do that to disengage taxi mode. not sure as to why you do that on boeings.
"...cannot the kingdom of salvation take me home."
 
Guest

RE: FR 738 Take Off

Sun Nov 16, 2003 1:27 am

The procedure to set takeoff power is basically the same in all airplanes.
After line-up on the runway, you advance the power levers to somewhat of a "higher" N1 or EPR power setting, this to "spool up" the engines, meaning by that that many bleed valves close at such a power setting.
xxx
When the engines are stabilized, and "spooled", a quick look at the numbers indicated (the flight engineer, in my old 747), the PF sets the takeoff power, from "spooled up", engines generally accelerate equally, and "adjustments" are done by our flight engineer.
xxx
At 80 kts, we put the "auto throttle" switch ON if we want to use it.
xxx
For our airplanes (we use EPR since we have JT9D-7Q engines) we set the "takeoff EPR" initially (that number is valid up to 80 kts), should the flight engineer need to "adjust" the power beyond 80 kts, he would have to use the "go around EPR" (somewhat lower number) since using straight "takeoff EPR" above 80 kts would possibly exceed the EPR limit of the engine...
xxx
Each engines are somewhat different, but the procedures are equivalent. I have flown airplanes with JT3D, JT4A, JT8D, JT9D, CF6 and CFM engines, while numbers are obviously different, the procedures remain the same.
xxx
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wing
Posts: 1357
Joined: Sun Oct 01, 2000 9:10 pm

RE: FR 738 Take Off

Sun Nov 16, 2003 2:51 am

On 737 autothrotle is set to ARM position when the aircraft lined up with the centerline.Then the PF takes the controls advances the throttles to aproximetely 40 % N1.when both engines spooled up equally and stabilised you press the TO/GA then the A/T advances the thrust lever to desired N1 setting.That helps pilot to see if the engines responding normally and avoids uneven throttle movement which can cause loss of allignment with the runway centerline.
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AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: FR 738 Take Off

Mon Nov 17, 2003 12:43 am

the pilots add thrust to the engines, then they reduce it quite a lot,

I suspect the reduced sound you hear is the engines nearly matching RPMs at the ~40% spool up point. Any change in the CFM56 engine's RPM causes a fairly significant increase in noise compared to any stable RPM noise level. An engine noise level decrease is noticable even in the cockpit whenever I allow the engines to fully stabilize prior to advancing to T/O power --normally I don't wait for a complete stabilization, but rather just "close enough" to know they will spool up without problem(s).

FWIW, a rolling takeoff is the standard takeoff procedure at AA. As pointed out earlier, 99+% of the runways we use are a lot longer than "balanced field length."
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